#include<bits/stdc++.h>
using namespace std;
long long jc(long long a){
	long long ans = 1;
	for(long long i = 1 ; i <= a ; i++){
		ans = ans * i;
	}
	return ans;
}
long long zhs(long long a , long long b){
	long long ans;
	ans = jc(a) / jc(b) / jc(a - b);
	return ans;
}
int main(){
	freopen("comb.in" , "r" , stdin);
	freopen("comb.out" , "w" , stdout);
	long long m , n;
	long long s;
	cin >> m >> n;
	s = zhs(m , n);
	cout << s << endl;
	return 0;
}